Author Katsura Hoshino commented that the upcoming series will continue the story from the first anime:

Thanks to everyone who went to the D.Gray-man stage today. As was said in the announcement, a new series has been green-lit. Because the staff will be completely different, the story will be a continuation, but I think it will become a completely new D.Gray-man anime. Thank you for everyone who’s supported me until now.

The 2016 anime will contain a brand new cast than the previous 2006 anime, that will include:

The anime’s website has also revealed that TMS Entertainment (Yowamushi Pedal,Detective Conan) will return to animate the series.

The first promotional video has also been released

Here is the 2016 anime’s main visual:

D.Gray-man is an action adventure manga written and illustrated by Katsura Hoshino. The series began in 2004 in Shueisha’s Weekly Shonen Jump magazine and is still currently ongoing in Jump SQ.Crown magazine, where a total of 24 volumes have been produced. The manga itself has sold over 22.5 million copies, with the last volume releasing in November 2013. The series received a light novel spin-off titled D.Gray-man: Reverse that ran from 2005 till 2010 for 3 volumes. The series also received a TV anime adaptation in 2006 produced by TMS Entertainment (Yowamushi Pedal, Detective Conan) and directed by Osamu Nabeshima (Yowamushi Pedal, Hamtaro).

Here is the series synopsis from MAL:

Toward the end of the 19th century, Allen Walker officially joins the organization of Exorcists that destroy the beings known as Akuma; mechanic weapons made by the Millennium Earl with the suffering souls of the dead. Allen has both a cursed eye and an anti-Akuma weapon as an arm, bearing the power of “Innocence,” a gift given to him as an apostle of God. Allen, along with his fellow Exorcists must put a stop to the Millennium Earl’s ultimate plot that could lead to the destruction of the world and all who live on it.

A brand new TV anime adaptation of D.Gray-man has been green-lit and will continue the story from the first anime. Additional details about the new anime will be revealed soon.